1. Field of the Invention
The present invention is generally directed to new methods and compositions for the delivery and uptake of therapeutic agents. The invention further provides new compositions for the treatment of disorders relating to increased activity or expression of myeloperoxidase.
2. Background of the Related Art
In the field of pharmaceutical and therapeutic intervention and treatment of disease states, a wide variety of macromolecular therapeutic agents have been developed, including proteins, peptides, nucleosides; nucleotides, antiviral agents, antineoplastic agents, antibiotics, etc., and prodrugs, precursors, derivatives and intermediates thereof. However, in order to be effective, such agents need to be delivered to the appropriate site of action. However, systemic delivery of such agents is often limited to the parenteral route of administration because such agents are typically extensively eliminated when administered orally. Even when administered parenterally, the uptake of many therapeutic agents at the target site of action is often limited by the inability of the therapeutic agent to get into the cellular site of action of the agent.
Thus, although many therapeutic agents have been tested in vitro, such agents frequently perform much less effectively in vivo where the agent must reach its target cells in a tissue in sufficient quantities to be potent while sparing bystander to their intended target sites of pharmacological action, namely, the cells inside the tissue (Jain, Nat. Med. 4, 655-657, 1998; Miller and Vile, FASEB J. 9, 190-199, 1995; Thrush et al., Annu. Rev. Immunol. 14, 49-71, 1995; Tomlinson, Adv. Drug Delivery Rev. 1, 87-198, 1987). For example, poor tissue penetration has hindered many monoclonal antibodies from reaching their cell-specific antigens to achieve effective tissue- or cell-directed pharmaco-delivery in vivo (Jain, Nat. Med. 4, 655-657, 1998, Thrush et al., Annu. Rev. Immunol. 14, 49-71, 1995; Tomlinson, Adv. Drug Delivery Rev. 1, 87-198, 1987; Dvorak et al., Cancer Cells 3, 77-85, 1991; Weinstein and van Osdol, Int. J. Immunopharmacol. 14, 457-463, 1992).
Another barrier to the uptake and delivery of blood-borne molecules a cellular site of action is the microvascular endothelium (Schnitzer, Trends Cardiovasc. Med. 3, 124-130, 1993; Renkin, J. Appl. Physiol. 134, 375-382, 1985). It is thought that there are specific transport mechanisms for the transendothelial transport of essential circulating blood macromolecules into the subendothelial space to meet the metabolic needs of the surrounding tissue cells (Schnitzer, Trends Cardiovasc. Med. 3, 124-130, 1993). Within the continuous endothelium there are distinct structures called caveolae. These flask-shaped invaginations in the plasma membrane of endothelial cells are open to the luminal blood vessel space and, therefore, accessible to molecules circulating in the blood vessel luminal space.
Caveolae may provide a trafficking pathway for macromolecules into and possibly across cells (Schnitzer N. Engl. J. Med. 339, 472-474, 1998, Schnitzer, Trends Cardiovasc. Med. 3, 124-130, 1993). Certain morphological studies have shown there are few plasmalemmal vesicles that exist free and unattached to other membranes inside the cell. These studies have led to the conclusion that caveolae are not dynamic, but rather static structures (Severs et al., J. Cell Sci. 90, 341-348, 1988; Bundgard, FASEB J. 42, 2425-2430, 1983). Nevertheless, caveolae are able to bud from the plasma membrane via a dynamin-mediated, GTP-dependent fission process (Oh et al., J. Biol. Chem., 141, 101-114, 1998, Schnitzer et al., Science 274, 239-242, 1996), and these structures contain key functional docking and fusion proteins (Schnitzer et al., Science 274, 239-242, 1996; McIntosh et al., Am. J. Physiol. 277, H2222-H2232, 1999; Schnitzer et al., Science 269, 1435-1439, 1995; Schnitzer et al., J. Biol. Chem. 270, 14399-14404, 1995). However, those skilled in the art have acknowledged that the ability of caveolae to mediate transcytosis remains unproven (McIntosh et al., Proc. Nat'l Acad. Sci., USA 99 (4):1996-2001, 2002). Therefore, the use of caveolae to overcome cell barriers to facilitate efficient pharmacodelivery in vivo along with detailed knowledge of the molecular composition and tissue-specific differences has been acknowledged as unknown (McIntosh et al., Proc. Nat'l Acad. Sci., USA 99 (4):1996-2001, 2002.
Albumin is a predominant plasma protein responsible for maintaining the transendothelial oncotic pressure gradient and regulating the transport of fatty acids, steroids, thyroxin and amino acids. Albumin is transported by the caveolae, and this transport is a key determinant of transcellular endothelial permeability (Tiruppathi et al., J. Biol. Chem., 272:25968-25975, 1997; Minshall et al., J. Biol. Chem., 150:1057-1069, 2000; Vogel et al., Am. J. Physiol Lung Cell Mol. Physiol. 281:L1512-L1522, 2001; John et al., Am. J. Physiol Lung Cell. Mol. Physiol. 284:L187-L196, 2003). The binding of albumin to Albumin-Binding Proteins (ABPs) localized in caveolae is essential for the transcellular permeability of albumin (Tiruppathi et al., J. Biol. Chem., 272:25968-25975, 1997; Minshall et al., J. Biol. Chem., 150:1057-1069, 2000; Vogel et al., Am. J. Physiol Lung Cell Mol. Physiol. 281:L1512-L1522, 2001; John et al., Am. J. Physiol Lung Cell. Mol. Physiol. 284:L187-L196, 2003). The ability of certain motifs or domains of peptides or proteins to interact with specific membrane components, followed by cellular uptake of the protein:receptor complex may point towards the potential application of such motifs in facilitating the delivery of drugs. However, the identity of these motifs remains to be determined for many proteins. In addition there remains a need to enhance the transport of an active agent through the endothelial lining of tissues. The identification of motifs of proteins that interact with cellular receptors and structures and allow the intracellular transport of those proteins and the subsequent binding of those motifs to active agents provides an elegant method of achieving enhanced transport active agents to which such motifs are conjugated.